Being nine years older, she would wipe the floor with her sister. But Vicky was determined to hold her own – by any means at her disposal.

“She’d turn the dice,” Christine says. “I knew what she was doing! Our younger brother would storm out of the room in tears.”

Christine laughs and breaks into that famous toothy smile she has flashed so often after triumphantly crossing the finishing line.

(Image: Getty)

Now the sisters – the only girls of eight kids – are starting to compete on a different stage. Vicky, 21, has followed in Christine’s speedy footsteps into athletics, and is also specialising in the 400m.

She shares Christine’s coach, is seen as a rising star and this week they will travel to the Glasgow 2014 Commonwealth Games as part of the England 400m senior squad.

Neither will compete individually – Christine is not in peak form – but they may end up passing the baton between them in the relay.

And at the Rio Olympics in 2016 things really could get heated, as both hope to compete in the singles race. Due to Christine’s recent poor form, Vicky is currently ranked higher.

“You know, I hope she is more successful than me,” she says slowly. “No matter what, I will always be her sister first and athlete second and if she did beat me I would be proud of her because to beat me you are beating the best guys in the world.”

But there is still steel in Christine’s smile. She’s determined to be the best, and ultimately, she tells me, she and Vicky will be “doing a job”.

She says: “I want my sister to run well, I want all the runners to – because that will make me run faster.”

(Image: Julian Andrews/ Sunday Mirror)

It must be tough watching a younger sibling gain strength as you battle for form at the age of 30. But Christine has sympathy for Vicky.

“It’s probably difficult for her being my sister,” she says. “I don’t want her to live in my shadow for the rest of her life. But she’s a tough cookie and I’m there to support her and try to help as much as I can.”

You sense it’s a bit of a juggling act for Christine being both the loving big sister and her baby sister’s rival.

But Christine is adamant having Vicky close by at the Commonwealth Games every day won’t distract her from the job in hand.

She doesn’t pull any punches when she says: “It is strictly business. Afterwards we will celebrate together but on the way there we keep our heads down.

"I won’t avoid her but she has a job to do. She has to stand on her own two feet.”

Off the track, it’s clear the strikingly similar sisters are close. Christine, who lives near the family home where Vicky remains, says: “She’s funnier than me, and feistier. And she’s more creative, arty.

“She’s a lot more forthright than me, she has quite a sharp tongue, whereas I might be more diplomatic. She doesn’t suffer fools gladly and she’ll let you know that.”

(Image: Rex)

Christine pauses for a second, then laughs: “She probably wouldn’t to me, though. I’m still her big sister, so she has to watch her mouth!

“But we have similar standards, we expect high standards from our work. We are like friends. Vicky’s a lot older than her years so I do talk to her on a level.

“She’s a lot of fun to be with. If I have an event I take her, or she hangs at my house, we watch TV – although she’s growing up now and I have to accept she has her own friends. I have to let her go – I can’t cramp her style.

“But we talk all the time. It’s weird, whenever I check my phone randomly when it’s on silent, she’s always calling. It’s like a sixth sense.”

The sisters grew up close to where the 2012 Olympic stadium is now, with their six brothers and computer engineer father Jonathan, and mother Patience, who works in the Inland Revenue.

Christine says it wasn’t her parents who pushed her into sports, she just loved it and was enticed by enthusiastic teachers.

In 2003 she won bronze in the 400m European Junior Championships. Three years later she won gold at the 2006 Commonwealth Games.

There have been tough times – particularly when, soon afterwards, she was suspended from competing for one year after missing three drugs tests, although there was no allegation she had done it deliberately.

When the ban ended she bounced back by scooping gold in the 2007 World Championships and gold at the Beijing Olympics in 2008.

(Image: Mirrorpix)

Vicky recalls her and her family’s excitement at watching Christine succeed.

She’s said: “Most of the time we watch Christine race at home. It’s just manic. Everyone gets proper nervous” She adds: “I’m quite fortunate, there aren’t many people in my position.”

She’s definitely fortunate. Christine admits she has helped fund her sister’s training. If Vicky can keep her head down and keeps progressing, her coach believes she may even have the ability to out-run her sister – although that will take a lot.

Christine produced her personal best time of 49.41sec last year at the Moscow World Championships, her second world title. But this year she has taken a step back.

She’s had a problem with her achilles heel which, in part, she freely admits might be down to her love of high heels.

“I do like getting dressed up, you spend six days a week in your kit, it’s nice to come home and wear something completely different,” she says.

She’s tried to take it as an opportunity to relax a bit, before stepping up for Rio. But, ever conscientious, Christine admits she’s struggled to take it easy.

“I am taking care of my personal life, but I have to make sure I’m not jeopardising my progress. And now we are in the midst of an important training period, so it’s pretty disciplined.”

All of which makes it tricky to form a relationship. Vicky has a boyfriend, but her older sister remains single – although she says she’d like a family.

“I have kind of found time for dating this year but you never fully step away from the sport. I have to be disciplined so I will be ready to go to Rio,” she says.

“It’s hard for men to understand my commitment unless they’re in sport. I have to call it an early night, go home early. People struggle to understand that generally.”

Luckily, one person who does understand is Vicky. After all those years with her head down, it must be a relief for Christine to share the load.

“It’s really fun when we train together,” Christine admits. “I think she’s great, it’s my dream she goes out and does the best she can. I will be her biggest fan forever.”

Christine Ohuruogu will compete at Glasgow 2014 Commonwealth Games and is an ambassador for Presenting Partner for Athletics, Virgin Media. Find out how Virgin Media is supercharging the Games by visiting www.virginmedia.com/glasgow2014